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The
Skeleton
The Skeleton
• The skeleton can be
divided in two main
regions:
– Axial
• Skull
• Vertebral column
• Bony thorax
– Appendicular
• made up of the bones of the limbs and their
girdles
The Axial Skeleton
• Eighty bones segregated
into three regions
– Skull
– Vertebral column
– Bony thorax
The Axial Skeleton
• Eighty bones segregated
into three regions
– Skull
– Vertebral column
– Bony thorax
The Skull
• The skull, the body’s most
complex bony structure, is
formed by two divisions the …
– Cranium
• protects the brain
– Facial bones
• Supply the framework of the
face, the sense organs, and
the teeth
• Provide openings for the passage of air
and food
• Anchor the facial muscles of expression
Anatomy of the Cranium
• Eight cranial bones – two parietal, two
temporal, frontal, occipital, sphenoid, and
ethmoid
• Cranial bones are
thin and remarkably
strong for their weight
Skull: Anterior View
Skull: Posterior View
Parietal Bones and Major
Associated Sutures
• Form most of the superior and lateral aspects of the skull
Parietal Bones and Major
Associated Sutures
• Four sutures mark the articulations
of the parietal bones
– Coronal suture – articulation
between parietal bones and
frontal bone anteriorly
– Sagittal suture – where right and
left parietal bones meet
superiorly
– Lambdoid suture – where
parietal bones meet the occipital
bone posteriorly
– Squamosal or squamous suture
– where parietal and temporal
bones meet
Occipital Bone and Its Major
Markings
Temporal Bones
• Form the inferolateral aspects of the skull and
parts of the cranial floor
• Divided into four major regions – squamous,
tympanic, mastoid, and petrous
• Major markings include the zygomatic, styloid,
and mastoid processes, and the mandibular and
middle cranial fossae
• Major openings include the stylomastoid and
jugular foramina, the external and internal
auditory meatuses, and the carotid canal
Temporal
Bones
Sphenoid Bone
• Butterfly-shaped bone that spans the width of
the middle cranial fossa
• Forms the central wedge that articulates with all
other cranial bones
• Consists of a central body, greater wings, lesser
wings, and pterygoid processes
• Major markings: the sella turcica, hypophyseal
fossa, and the pterygoid processes
• Major openings include the foramina rotundum,
ovale, and spinosum; the optic canals; and the
superior orbital fissure
Sphenoid Bone
Ethmoid Bone
• Most deep of the skull bones; lies between
the sphenoid and nasal bones
• Forms most of the bony area between the
nasal cavity and the orbits
• Major markings include the cribriform
plate, crista galli, perpendicular plate,
nasal conchae, and the ethmoid sinuses
Ethmoid Bone
Wormian Bones
• Tiny irregularly shaped bones that appear
within sutures
Facial Bones
• Fourteen bones of which only the
mandible and vomer are unpaired
• The paired bones are the maxillae,
zygomatics, nasals, lacrimals, palatines,
and inferior conchae
Anterior Aspects of the Skull
Facial Bones
Mandible and Its Markings
Maxillary Bones
• Medially fused bones that make up the
upper jaw and the central portion of the
facial skeleton
• Facial keystone bones that articulate with
all other facial bones except the mandible
• Their major markings include palatine,
frontal, and zygomatic processes, the
alveolar margins, inferior orbital fissure,
and the maxillary sinuses
Maxillary Bone
Zygomatic Bones
• Irregularly shaped bones (cheekbones)
that form the prominences of the cheeks
and the inferolateral margins of the orbits
Other Facial Bones
• Nasal bones – thin medially fused bones
that form the bridge of the nose
• Lacrimal bones – contribute to the medial
walls of the orbit and contain a deep
groove called the lacrimal fossa that
houses the lacrimal sac
• Palatine bones – two bone plates that form
portions of the hard palate, the
posterolateral walls of the nasal cavity,
and a small part of the orbits
Other Facial Bones
• Vomer – plow-shaped bone that forms part
of the nasal septum
• Inferior nasal conchae – paired, curved
bones in the nasal cavity that form part of
the lateral walls of the nasal cavity
Anterior Aspects of the Skull
Posterior Aspects of the Skull
External Lateral Aspects of the
Skull
Midsagittal Lateral Aspects of
the Skull
Inferior Portion of the Skull
Inferior Portion of the Skull
Orbits
• Bony cavities in which the eyes are firmly
encased and cushioned by fatty tissue
• Formed by parts of seven bones – frontal,
sphenoid, zygomatic, maxilla, palatine,
lacrimal, and ethmoid
Orbits
Nasal Cavity
• Constructed of bone and hyaline cartilage
• Roof – formed by the cribriform plate of
the ethmoid
• Lateral walls – formed by the superior and
middle conchae of the ethmoid, the
perpendicular plate of the palatine, and the
inferior nasal conchae
• Floor – formed by palatine process of the
maxillae and palatine bone
Paranasal Sinuses
• Mucosa-lined, air-filled sacs found in five
skull bones – the frontal, sphenoid,
ethmoid, and paired maxillary bones
• Air enters the paranasal sinuses from the
nasal cavity and mucus drains into the
nasal cavity from the sinuses
• Lighten the skull and enhance the
resonance of the voice
Paranasal Sinuses
Hyoid Bone
• Not actually part of the skull, but lies just
inferior to the mandible in the anterior
neck
• Only bone of the body that does not
articulate directly with another bone
• Attachment point for neck muscles that
raise and lower the larynx during
swallowing and speech
Hyoid
Vertebral Column
• Formed from 26 irregular bones
(vertebrae) connected in such a way that a
flexible curved structure results
– Cervical vertebrae – 7 bones of the neck
– Thoracic vertebrae – 12 bones of the torso
– Lumbar vertebrae – 5 bones of the lower back
– Sacrum – bone inferior to the lumbar
vertebrae that articulates with the hip bones
Vertebral
Column
Vertebral Column: Curvatures
• Posteriorly concave curvatures – cervical
and lumbar
• Posteriorly convex curvatures – thoracic
and sacral
• Abnormal spine curvatures include
scoliosis (abnormal lateral curve),
kyphosis (hunchback), and lordosis
(swayback)
Vertebral Column: Ligaments
• Anterior and posterior longitudinal
ligaments – continuous bands down the
front and back of the spine from the neck
to the sacrum
• Short ligaments connect adjoining
vertebrae together
Vertebral Column: Ligaments
Vertebral Column: Intervertebral
Discs
• Cushionlike pad composed of two parts
– Nucleus pulposus – inner gelatinous nucleus
that gives the disc its elasticity and
compressibility
– Annulus fibrosus – surrounds the nucleus
pulposus with a collar composed of collagen
and fibrocartilage
Vertebral Column: Intervertebral
Discs
General Structure of Vertebrae
• Body or centrum – discshaped, weight-bearing region
• Vertebral arch – composed of
pedicles and laminae that,
along with the centrum,
enclose the vertebral foramen
• Vertebral foramina – make up
the vertebral canal through
which the spinal cord passes
General Structure of Vertebrae
• Body or centrum – discshaped, weight-bearing region
• Vertebral arch – composed of
pedicles and laminae that,
along with the centrum,
enclose the vertebral foramen
• Vertebral foramina – make up
the vertebral canal through
which the spinal cord passes
General Structure
of Vertebrae
• Spinous processes
project posteriorly, and
transverse processes
project laterally
• Intervertebral foramina –
lateral openings formed
from notched areas on
the superior and inferior
borders of adjacent
pedicles
General Structure of Vertebrae
Cervical Vertebrae
• Seven vertebrae (C1-C7) are the smallest,
lightest vertebrae
• C3-C7 are distinguished with an oval body,
short spinous processes, and large,
triangular vertebral foramina
• Each transverse process contains a
transverse foramen
Cervical
Vertebrae
Cervical Vertebrae: The Atlas
(C1)
• The atlas has no body and no spinous
process
• It consists of anterior and posterior arches,
and two lateral masses
• The superior surfaces of lateral masses
articulate with the occipital condyles
Cervical Vertebrae: The Atlas (C1)
Cervical Vertebrae: The Axis
(C2)
• The axis has a body, spine, and vertebral
arches as do other cervical vertebrae
• Unique to the axis is the dens, or odontoid
process, which projects superiorly from the
body and is cradled in the anterior arch of
the atlas
• The dens is a pivot for the rotation of the
atlas
Cervical Vertebrae: The Axis (C2)
Cervical Vertebrae: The Atlas (C2)
Thoracic Vertebrae
• There are twelve vertebrae (T1-T12) all of
which articulate with ribs
• Major markings include two facets and two
demifacets on the heart-shaped body, the
circular vertebral foramen, transverse
processes, and a long spinous process
• The location of the articulate facets
prevents flexion and extension, but allows
rotation of this area of the spine
Thoracic Vertebrae
Lumbar Vertebrae
• The five lumbar vertebrae (L1-L5) are
located in the small of the back and have
an enhanced weight-bearing function
• They have short, thick pedicles and
laminae, flat hatchet-shaped spinous
processes, and a triangular-shaped
vertebral foramen
• Orientation of articular facets locks the
lumbar vertebrae together to provide
stability
Lumbar Vertebrae
Sacrum
• Sacrum
– Consists of five fused vertebrae (S1-S5),
which shape the posterior wall of the
pelvis
– It articulates with L5 superiorly, and with
the auricular surfaces of the hip bones
– Major markings include the sacral
promontory, transverse lines, alae,
dorsal sacral foramina, sacral canal, and
sacral hiatus
Coccyx
• Coccyx
(Tailbone)
– The coccyx is
made up of four
(in some cases
three to five)
fused vertebrae
that articulate
superiorly with
the sacrum
Sacrum and Coccyx: Posterior
View
Bony Thorax (Thoracic Cage)
• The thoracic cage is composed of the
thoracic vertebrae dorsally, the ribs
laterally, and the sternum and costal
cartilages anteriorly
• Functions
– Forms a protective cage around the heart,
lungs, and great blood vessels
– Supports the shoulder girdles and upper limbs
– Provides attachment for many neck, back,
chest, and shoulder muscles
– Uses intercostal muscles to lift and depress
the thorax during breathing
Bony Thorax (Thoracic Cage)
Bony Thorax (Thoracic Cage)
Sternum (Breastbone)
• A dagger-shaped, flat bone that lies in the
anterior midline of the thorax
• Results from the fusion of three bones –
the superior manubrium, the body, and the
inferior xiphoid process
• Anatomical landmarks include the jugular
(suprasternal) notch, the sternal angle,
and the xiphisternal joint
Ribs
• There are twelve pair of ribs forming the flaring
sides of the thoracic cage
• All ribs attach posteriorly to the thoracic
vertebrae
• The superior 7 pair (true, or vertebrosternal ribs)
attach directly to the sternum via costal
cartilages
• Ribs 8-10 (false, or vertebrocondral ribs) attach
indirectly to the sternum via costal cartilage
• Ribs 11-12 (floating, or vertebral ribs) have no
anterior attachment
Ribs
Structure of a Typical True Rib
• Bowed, flat
bone consisting
of a head,
neck, tubercle,
and shaft
Figure 7.20
Appendicular Skeleton
• The appendicular skeleton is made up of
the bones of the limbs and their girdles
• Pectoral girdles attach the upper limbs to
the body trunk
• Pelvic girdle secures the lower limbs
Appendicular
Skeleton
Pectoral Girdles (Shoulder
Girdles)
• The pectoral girdles consist of the anterior
clavicles and the posterior scapulae
• They attach the upper limbs to the axial
skeleton in a manner that allows for
maximum movement
• They provide attachment points for
muscles that move the upper limbs
Pectoral
Girdles
(Shoulder
Girdles)
Clavicles (Collarbones)
• The clavicles are slender, doubly curved
long bones lying across the superior
thorax
• The acromial (lateral) end articulates with
the scapula, and the sternal (medial) end
articulates with the sternum
• They provide attachment points for
numerous muscles, and act as braces to
hold the scapulae and arms out laterally
away from the body
Clavicles (Collarbones)
Scapulae (Shoulder Blades)
• The scapulae are triangular, flat bones
lying on the dorsal surface of the rib cage,
between the second and seventh ribs
• Scapulae have three borders and three
angles
• Major markings include the suprascapular
notch, the supraspinous and infraspinous
fossae, the spine, the acromion, and the
coracoid process
• These are important landmarks for
auscultation
Scapulae (Shoulder Blades)
The Upper Limb
• The upper limb consists of the arm
(brachium), forearm (antebrachium), and
hand (manus)
• Thirty-seven bones form the skeletal
framework of each upper limb
Arm
• The humerus is the sole bone of the arm
• It articulates with the scapula at the
shoulder, and the radius and ulna at the
elbow
Arm
• Major markings
– Proximal humerus includes the head,
anatomical and surgical necks, greater and
lesser tubercles, and the intertubercular
groove
– Distal humerus includes the capitulum,
trochlea, medial and lateral epicondyles, and
the coronoid and olecranon fossae
– Medial portion includes the radial groove and
the deltoid process
Humerus of the Arm
Forearm
• The bones of the forearm are the radius
and ulna
• They articulate proximally with the
humerus and distally with the wrist bones
• They also articulate with each other
proximally and distally at small radioulnar
joints
• Interosseous membrane connects the two
bones along their entire length
Bones of the Forearm
Ulna
• The ulna lies medially in the forearm and
is slightly longer than the radius
• Forms the major portion of the elbow joint
with the humerus
• Its major markings include the olecranon,
coronoid process, trochlear notch, radial
notch, and the styloid process
Radius
• The radius lies opposite (lateral to) the
ulna and is thin at its proximal end,
widened distally
• The superior surface of the head
articulates with the capitulum of the
humerus
• Medially, the head articulates with the
radial notch of the ulna
• Major markings include the radial
tuberosity, ulnar notch, and styloid process
Radius and Ulna
• Skeleton of
the hand
contains wrist
bones
(carpals),
bones of the
palm
(metacarpals),
and bones of
the fingers
(phalanges)
Hand
Carpus (Wrist)
• Consists of eight
bones
– Scaphoid, lunate,
triquetral, and
pisiform proximally
– Trapezium, trapezoid,
capitate, and hamate
distally
Metacarpus (Palm)
• Five numbered (1-5) metacarpal bones
radiate from the wrist to form the palm
– Their bases articulate with the carpals
proximally, and with each other medially and
laterally
– Heads articulate with the phalanges
Phalanges (Fingers)
• Each hand contains 14 miniature long
bones called phalanges
• Fingers (digits) are numbered 1-5,
beginning with the thumb (pollex)
• Each finger (except the thumb) has three
phalanges – distal, middle, and proximal
• The thumb has no middle phalanx
Pelvic Girdle (Hip)
• The hip is formed by a pair of hip bones
(os coxae, or coxal)
• Together with the sacrum and the coccyx,
these bones form the bony pelvis
• The pelvis
– Attaches the lower limbs to the axial skeleton
with the strongest ligaments of the body
– Transmits weight of the upper body to the
lower limbs
– Supports the visceral organs of the pelvis
Pelvic Girdle (Hip)
Ilium
• The ilium is a large flaring bone that forms
the superior region of the coxal bone
• It consists of a body and a superior winglike
portion called the ala
• The broad posterolateral surface is called
the gluteal surface
• The auricular surface articulates with the
sacrum (sacroiliac joint)
• Major markings include the iliac crests, four
spines, greater sciatic notch, iliac fossa,
arcuate line, and the pelvic brim
Ilium: Lateral View
Ilium: Medial View
Ischium
• The ischium forms the posteroinferior part
of the hip bone
• The thick body articulates with the ilium,
and the thinner ramus articulates with the
pubis
• Major markings include the ischial spine,
lesser sciatic notch, and the ischial
tuberosity
Pubis
• The pubic bone forms the anterior portion
of the hip bone
• It articulates with the ischium and the ilium
• Major markings include superior and
inferior rami, the pubic crest, pubic
tubercle, pubic arch, pubic symphysis, and
obturator foramen (along with ilium and
ischium)
Pubis: Lateral View
Pubis: Medial View
Comparison of Male and
Female Pelvic Structure
• Female pelvis
– Tilted forward, adapted for childbearing
– True pelvis defines birth canal
– Cavity of the true pelvis is broad, shallow, and
has greater capacity
Comparison of Male and
Female Pelvic Structure
• Male pelvis
– Tilted less forward
– Adapted for support of heavier male build and
stronger muscles
– Cavity of true pelvis is narrow and deep
Comparison of Male and
Female Pelvic Structure
Comparison of Male and
Female Pelvic Structure
Characteristic
Female
Male
Bone thickness
Lighter, thinner, and smoother
Heavier, thicker, and
more prominent
markings
Pubic arch/angle
80˚–90˚
50˚–60˚
Acetabula
Small; farther apart
Large; closer together
Sacrum
Wider, shorter; sacral curvature
is accentuated
Narrow, longer; sacral
promontory more ventral
Coccyx
More movable; straighter
Less movable; curves
ventrally
The Lower Limb
• The three segments of the lower limb are
the thigh, leg, and foot
• They carry the weight of the erect body,
and are subjected to exceptional forces
when one jumps or runs
Femur
• The sole bone of the thigh is the femur,
the largest and strongest bone in the body
• It articulates proximally with the hip and
distally with the tibia and fibula
• Major markings include the head, fovea
capitis, greater and lesser trochanters,
gluteal tuberosity, lateral and medial
condyles and epicondyles, linea aspera,
patellar surface, and the intercondylar
notch
Femur
Leg
• The tibia and fibula form the skeleton of
the leg
• They are connected to each other by the
interosseous membrane
• They articulate with the femur proximally
and with the ankle bones distally
• They also articulate with each other via the
immovable tibiofibular joints
Tibia
• Receives the weight of the body from the
femur and transmits it to the foot
• Major markings include medial and lateral
condyles, intercondylar eminence, the
tibial tuberosity, anterior crest, medial
malleolus, and fibular notch
Tibia and Fibula
Fibula
• Sticklike bone with slightly expanded ends
located laterally to the tibia
• Major markings include the head and
lateral malleolus
• It is not the Fibia
Foot
• The skeleton of
the foot includes
the tarsus,
metatarsus, and
the phalanges
(toes)
• The foot supports
body weight and
acts as a lever to
propel the body
forward in walking
and running
Tarsus
• Composed of seven bones that form the
posterior half of the foot
• Body weight is carried primarily on the
talus and calcaneus
• Talus articulates with the tibia and fibula
superiorly, and the calcaneus inferiorly
• Other tarsus bones include the cuboid and
navicular, and the medial, intermediate,
and lateral cuneiforms
Tarsus
Calcaneus
• Forms the heel of the foot
• Carries the talus on its superior surface
• Point of attachment for the calcaneal
(Achilles) tendon of the calf muscles
Metatarsus and Phalanges
• Metatarsals
– Five (1-5) long bones that articulate with the
proximal phalanges
– The enlarged head of metatarsal 1 forms the
“ball of the foot”
• Phalanges
– The 14 bones of the toes
– Each digit has three phalanges except the
hallux, which has no middle phalanx
Metatarsus and Phalanges
Arches of the Foot
• The foot has three arches maintained by
interlocking foot bones and strong
ligaments
• Arches allow the foot to hold up weight
• The arches are:
– Lateral longitudinal – cuboid is keystone of
this arch
– Medial longitudinal – talus is keystone of this
arch
– Transverse – runs obliquely from one side of
the foot to the other
Arches of the Foot